This protocol has been registered with the International Prospective Register for Systematic Reviews (PROSPERO) on the 10 July 2012 under registration number CRD42012002621 (Available online from http://www.crd.york.ac.uk/prospero/display_record.asp?ID=CRD42012002621). This protocol comprises an addition of an existing systematic review report: Mickenautsch S, Yengopal V. Failure rate of atraumatic restorative treatment using high-viscosity glass-ionomer cement compared to conventional amalgam restorative treatment in primary and permanent teeth: a systematic review update - III. J Minim Interv Dent 2012; 5: 273-331 and provides a quantitative systematic review of the Chinese literature to the topic.

Review question : This systematic review seeks to answer the question as to whether, in patients with carious cavities of any class in primary and permanent teeth, ART restorations have a higher failure rate than amalgam restorations placed using conventional rotary instruments in tooth cavities of the same size, type of dentition and followup period?
Systematic literature search : Databases: Chinese Biomedical Literature Database (CBM), Chinese Medical Current Content (CMCC), China National Knowledge Infrastructure (CNKI, formerly China Academic Journals), VIP Information and WanFang Data; searching of reference lists of included articles.
Search term development : Strings of search terms will be constructed in simplified Chinese. In addition, the English search term "atraumatic restorative treatment" will be used for database search.
Article selection criteria : Clinical trials (trials on animals, in-situ, in-vitro trials not included); Controlled trials: including control- and test group(s) (1-arm longitudinal trials not included); Trial focus relevant to the review question; Prospective trials (retrospective trials not included).
Data extraction : The information extracted from trials will include general trial information, intervention integrity, methodological quality and bias risk; all data with relevance to the review question will be extracted in form of individual dichotomous and continuous datasets.
Data analysis and reporting : A relative point estimate (RR = Risk ratio) will be computed, the results will also be converted into an absolute outcome measure (RD = Risk difference), as well as into an illustrative comparative risk for both, test- and control intervention, and reported accordingly; statistical heterogeneity will be investigated; sensitivity analysis will be applied in order to establish whether all findings are robust to the type of data analysis used; Selection-, detection-, performance-, attrition-, publication- and reporting bias risk in the accepted trials will be assessed; Research gaps within accepted trials in terms of imprecision, inconsistency, lack of right information and shortcomings in bias risk control will be identified using a designated worksheet and subsequently more detailed recommendations for further research will be added to the this systematic review update.

Context : Selection bias interferes with the internal validity of clinical trials and leads to favoring one clinical outcome over another. Random sequence generation and allocation concealment of such sequence have been proposed to limit the risk of selection bias. However, selection bias can be introduced based on knowledge of the directly observed random sequence when allocation concealment is subverted. Such subversion may statistically be detected in randomised control trials with dichotomous outcomes through regression analysis of the reversed propensity score (RPS) sequence together with the sequence of the observed dichotomous outcome per patient.

Problem : Preliminary investigations have shown promising accuracy of RPS based selection bias testing in simulated randomised control trials (S-RCTs). However, these results were not presented in form of summary receiver operating characteristics (SROC) curves that may have eased the graphical recognition of the achieved test accuracy.
Suggested solution : The previously established total numbers of true negative/false positive (TN/FP) and true positive/false negative (TP/FN) results, per set alpha level, were entered into Meta-DiSc Version 1.4 statistical software and SROC curves per alpha level were generated. Initially, the SROC curve for alpha level 5% suggested higher test accuracy than for alpha 1%. However, the result may have been due to one data point outlier. Correction by removal of the outlier suggested test accuracy for alpha 1% > alpha 5% > alpha 20%. Further investigations to this topic are needed through well-designed statistical simulation studies.

Context : The dichotomous outcome of a clinical intervention may be defined as success versus failure and subsequently expressed in the number of intervention successes and failures. Success and failure numbers of two clinical interventions may be compared and the resulting effect estimate expressed either as Risk ratio (RR) or Odds ratio (OR) with 95% confidence intervals (CI). The expression of effect estimates in Risk ratio appears to be easier to interpret. Also, Risk ratio of success rates implies the "risk of success", which seems counter-intuitive from a linguistic point of view and it has been suggested that failures are of more interest for interventions that aim to heal or have positive effects, while successes or survivals are of more interest in circumstances of harm. Based on these considerations, the comparison of two intervention indented to heal based on their number of failures and the expression of the resulting effect estimate in Risk ratio, appears to be most appropriate.

Problem : Pure logical conjecture may not provide sufficient reason for choosing comparison of failures above successes and Risk ratio above Odds ratio and a more empirical basis for an informed choice is needed.
Suggested solution : The outcome of this brief investigation suggest that the use of Risk ratio for expressing differences in success rates may lead to statistically significant results when comparison of failure rates based of Risk ratio or the use of Odds ratios for failures and successes does not. These findings support the use of Risk ratio for failure rates instead of success rates for comparison of interventions that aim to heal in order to be easier interpretable and in order to avoid potentially misleading results.